Ranking print jobs based on transfer media healthy area

ABSTRACT

In an embodiment, a processor-readable medium stores code representing instructions that when executed by a processor cause the processor to access a list of print jobs for printing. The processor further determines a healthy area of a transfer media. For each job in the list, the processor calculates an image risk area (IRA) based on the healthy area, and ranks each job in a print order according to its IRA.

CLAIM FOR PRIORITY

The present application is a national stage filing under 35 U.S.C. §371of PCT application number PCT/EP2013/062810, having an internationalfiling date of Jun. 19, 2013, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND

Some printing devices, including liquid electro-photography (LEP)printing devices, employ image transfer media such as image transferblankets. An image transfer blanket receives images formed on a photoimaging member, or from an inkjet system or other digital means, andtransfers the images onto print media, such as cut sheet media or acontinuous media web. Blanket wear mechanisms related to the printedimages and the types of media substrates being used, cause the blanketto wear. As the number of same printed images increases, the blanketwear increases and eventually appears as a defect on other printedimages. In order to avoid this adverse impact on print quality, printingdevice operators often replace image transfer blankets at regularintervals once the number of printed images increases beyond a certainthreshold level. Furthermore, if blanket wear begins to cause defects onthe printed images prior to reaching the threshold, device operators arelikely to replace the image transfer blanket even sooner. Unfortunately,replacing image transfer blankets is expensive and reduces printeroutput efficiency because of the time involved in the replacement.

BRIEF DESCRIPTION OF THE DRAWINGS

The present embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 illustrates a printing device suitable for implementing a printjob ranking algorithm that ranks print jobs into a printing order basedon a healthy area of an image transfer blanket, according to an exampleimplementation;

FIG. 2 shows a box diagram of a controller suitable for implementing aprint job ranking algorithm within an LEP printing device, according toan example implementation;

FIG. 3 shows an image transfer blanket with a healthy area and an imagearea on which an image of a print job is to be printed, according to anexample implementation;

FIG. 4 shows a table that contains an example of blanket history data,according to an example implementation;

FIGS. 5a, 5b, and 5c show example results of calculations made by aprint job ranking algorithm to determine the presence of a wear defectand the resulting dimensions of the healthy area of an image transferblanket, according to example implementations

FIGS. 6, 7, and 8, show flowcharts of example methods related toimplementing a print job ranking algorithm that ranks print jobs into aprinting order based on a healthy area of an image transfer blanket,according to different example implementations.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

Overview

As noted above, image transfer blankets used in printing devices, suchas liquid electro-photography (LEP) printing devices, are typicallyreplaced on a periodic basis due to wear in the blankets caused by therepeated transfer of images onto print media and repeated interactionwith media. Blanket wear can cause defects in the transferred images,which in turn reduces overall print quality. One common example ofblanket wear is cut-marks that can develop on the blanket due to thesharp edges of the printed substrates (i.e., the print media). Therepeated pressing of the print media (e.g., paper) against the blanketcauses the sharp edges of the media to cut into the blanket.Subsequently, when images are printed in areas that extend beyond thecut-marks (e.g., when a larger image is printed), the ink in thecut-mark areas does not transfer well to the print media, and thecut-marks become visible as defects on the printed output. While thisdisclosure uses image transfer blankets as a typical example, theconcepts discussed herein are not limited in this regard, but areinstead intended to be broadly applicable to other currently existing orfuture developed image transfer members.

Another common example of wear to an image transfer blanket comes from“image memory” caused by previously printed images. If an image isprinted many times (i.e., the same image), so that ink is repeatedlyapplied to the same areas of the blanket while being repeatedly left offof other areas of the blanket, the blanket becomes damaged in thoseareas where no ink is being applied. Subsequently, when a differentimage is printed that calls for the application of ink onto the blanketin areas where ink has not been previously applied, the appearance ofthe printed image varies between those areas where ink had beenpreviously applied and those areas where ink had not been previouslyapplied.

The appearance of these and other wear mechanisms on printed output willtypically result in the replacement of an image transfer blanket byprinter device operators. However, replacing image transfer blankets isboth expensive and time consuming. In addition, replacing an imagetransfer blanket reduces the output efficiency of the printing device,because the printing device sits idle while the blanket is beingreplaced. Accordingly, efforts to reduce the impact of wear on imagetransfer blankets and improve the useful lifespan of blankets areongoing.

Embodiments of the present disclosure extend the useful lifespan of animage transfer blanket by prioritizing print jobs based on a healthyarea of the blanket and the likelihood that each job will not result invisible print defects when printed. Print jobs are ranked in a printorder from a lowest to highest risk that they will display a blanketrelated print defect. A job ranking algorithm evaluates historicalblanket data to determine when damage (i.e., a defect) is likely to bepresent on the blanket. When the algorithm determines a high enoughprobability of damage to the blanket, the algorithm then calculates anarea of the blanket that can be regarded as a healthy area. From a listof potential print jobs, the algorithm then generates a ranked printorder that prioritizes each job based on a relative risk that the jobwill have a print quality problem given the blanket's present conditionand healthy area. When the risk of a print quality problem is equivalentbetween one or more print jobs, the algorithm considers a second factorin generating the print order. The second factor considered is thepotential for each print job to cause additional damage to the blanketand further reduce the size of the blanket's healthy area.

In an example implementation, a processor-readable medium stores coderepresenting instructions that when executed by a processor cause theprocessor to access a list of print jobs for printing. The processordetermines a healthy area of a transfer media. Then, for each job in thelist, the processor calculates an image risk area (IRA) based on thehealthy area. The processor then ranks each job in a print orderaccording to its IRA.

In another example implementation, a processor-readable medium storescode representing instructions that when executed by a processor causethe processor to calculate a healthy area of an image transfer blanket.The processor then calculates an image risk area (IRA) as an amount ofimage area of a print job that falls outside of the healthy area of theimage transfer blanket. The processor then ranks the print job in aprint order so that it is above other print jobs having larger IRAs andbelow other print jobs having smaller IRAs.

In another example implementation, a processor-readable medium storescode representing instructions that when executed by a processor causethe processor to determine a healthy area of an image transfer blanket.The processor accesses a list of print jobs, with each print jobdefining an image area. For each print job, the processor determines animage risk area (IRA) that defines an amount of the image area thatfalls outside of the healthy area, and a potential damage area (PDA)that defines an amount of the healthy area that is not covered by theimage area. The processor then ranks the print jobs in a print orderbased on the IRA and PDA of each print job. In one example, theprocessor first ranks the print jobs from smallest IRA to largest IRA,and where two or more print jobs have equivalent IRAs, the processorranks the two or more print jobs from smallest PDA to largest PDA.

Illustrative Embodiments

FIG. 1 illustrates an example of a printing device 100 suitable forimplementing a print job ranking algorithm that prioritizes (i.e.,ranks) print jobs into a printing order based on a healthy area of animage transfer blanket and the likelihood that each job will not incurvisible print defects when printed. The printing device 100 comprises aprint-on-demand device, such as a liquid electro-photography (LEP)printer comprising an image transfer blanket (or other suitable imagetransfer media) that sustains wear from the repetitious transfer ofimages onto print media, as noted above. A printing device 100implemented as an LEP printer 100 includes a print engine 102 thatreceives print media 104 (e.g., cut-sheet paper) from a media inputmechanism 106, and outputs printed media 108 to a media output mechanism110. The print engine 102 includes a photo imaging component, such as aphoto imaging plate (PIP) 112 mounted on a drum or imaging cylinder 114.The PIP 112 defines an outer surface of the imaging cylinder 114 onwhich images can be formed. A charging component such as charge roller116 generates electrical charge that flows toward the PIP surface andcovers it with a uniform electrostatic charge.

A laser imaging unit 118 exposes image areas on the PIP 112, whichdissipates (neutralizes) the charge in those areas. Exposure of the PIPcreates a ‘latent image’ in the form of an invisible electrostaticcharge pattern that replicates the image to be printed. In a digital LEPprinting device 100, the image is created from digital image data thatrepresents words, pages, text and images that can be created, forexample, with electronic layout and/or desktop publishing programs. Acontroller 120 uses digital image data to control the laser imaging unit118 to selectively expose the PIP 112. Digital image data is generallyformatted as one or more print jobs stored and executed on controller120, as further discussed herein below.

Ink is then developed to the latent, electrostatic image on the PIP 112by binary ink development (BID) rollers 122, forming an ink image on theouter surface of the PIP 112. The ink image formed on the outer surfaceof the PIP 112 is electrically transferred to an image transfer blanket124, which is electrically charged through an intermediate drum ortransfer cylinder 126. The image transfer blanket 124 overlies, and issecurely attached to, the outer surface of the transfer cylinder 126.The transfer cylinder 126 is configured to heat the blanket 124, whichcauses the liquid in the ink to evaporate and the solid particles topartially melt and blend together, forming a hot adhesive liquidplastic. The heated ink image is then transferred to the print media104, which is held by an impression cylinder 128.

During the transfer from the image transfer blanket 124 to the printmedia 104, the print media 104 is pinched between the impressioncylinder 128 and the blanket 124 on the transfer cylinder 126. It is therepeated pressing of print media 104 by the impression cylinder 128 intothe image transfer blanket 124 that creates wear on the blanket 124.More specifically, the repeated impressions of print media 104 into theblanket 124 results in permanent deformations and defects in the blanket124 (e.g., cut-marks from print media edges) that can impact printquality. Once the ink image has been transferred to the print media 104,the printed media 108 is transported by various rollers 132 to theoutput mechanism 110.

FIG. 2 shows a box diagram of a controller 120 suitable for implementinga print job ranking algorithm within an LEP printing device 100.Controller 120 generally comprises a processor (CPU) 200 and a memory202, and may additionally include firmware and other electronics forcommunicating with and controlling the other components of print engine102, as well as media input and output mechanisms 106 and 110. Memory202 can include both volatile (i.e., RAM) and nonvolatile (e.g., ROM,hard disk, floppy disk, CD-ROM, etc.) memory components comprisingnon-transitory computer/processor-readable media that provide for thestorage of computer/processor-readable coded instructions, datastructures, program modules, JDF, and other data.

As noted above, controller 120 uses digital image data to control thelaser imaging unit 118 in the print engine 102 to selectively expose thePIP 112. More specifically, controller 120 receives print data 204 froma host system, such as a computer, and stores the data 204 in memory202. Data 204 represents, for example, documents or image files to beprinted. As such, data 204 forms one or more print jobs 206 for printingdevice 100 that each include print job commands and/or commandparameters. Using a print job 206 from data 204, controller 120 controlscomponents of print engine 102 (e.g., laser imaging unit 118) to formcharacters, symbols, and/or other graphics or images on print media 104.

In one implementation, controller 120 includes a print job rankingalgorithm 208 stored in memory 202. Print job ranking algorithm 208comprises instructions executable on processor 200 to determine a rankedor prioritized order for printing available print jobs 206. In oneexample, the algorithm 208 generates a ranked job print order list 210that places the jobs in a prioritized order for printing. In general,the ranking algorithm 208 ranks each of the print jobs 206 in aprioritized print order based on one or two (or more) factors associatedwith a calculated healthy area 212 of the image transfer blanket 124.The first factor is an image risk area (IRA) 214 calculated for eachprint job 206, and the second factor is a potential damage area (PDA)216, also calculated for each print job 206.

FIG. 3 shows an example of an image transfer blanket 124 with a healthyarea 300 and an image area 302 on which an image of a print job 206 isto be printed, according to one implementation. The image area 302 isdefined by the dashed line in FIG. 3. In this example, the image area302 is assumed to be the same size as the print media 104 substrate areaon which the image of a print job 206 is to be printed. Thus, both theimage area 302 and the print media 104 substrate are defined by thedashed line, as shown in FIG. 3. However, in other examples, the imagearea 302 may be smaller than the print media 104 substrate area. In suchcases, the size of an image from a print job 206 falls within the imagearea 302, but the image area 302 is smaller than the area of the printmedia 104 substrate and does not extend over the entire area of theprint media 104 substrate.

The healthy area 300 shown in FIG. 3 represents a graphical illustrationthat corresponds with the healthy area 212 numerical value calculatedand stored in the memory 202 as noted above regarding FIG. 2. Thehealthy area 300 of the blanket 124 represents an area of the blanketthat is capable of transferring images from the PIP 112 to the printmedia 104 without transferring defects from the blanket 124 to the media104. In general, areas outside of the healthy area 300 are unhealthy,and can result in defects being transferred to printed images. However,in some examples, unhealthy areas can also be confined within thehealthy area 300. Such a confined unhealthy area might arise due to theconstant printing of a label or other constant image. Therefore, thehealthy area 300 may not always be a complete region, but may includewithin it, an unhealthy area. The print job ranking algorithm 208determines the healthy blanket area 300 based on the blanket's historydata 218. The blanket history data 218 comprises data for each of theprint jobs previously printed on printing device 100.

FIG. 4 shows a table that contains an example of blanket history data218. Blanket history data 218 can include, for example, the lengths,widths, and thicknesses of previously printed pages, along with thenumber of impressions made on the blanket 124 by pages of varyingdimensions. Using the blanket history data 218, the ranking algorithm208 determines if there is a wear defect in the blanket 124 bycalculating a cumulative thickness of print media 104 that has beenimpressed onto the blanket 124 for the various sizes and types of printmedia 104 previously printed by printing device 100. Wear is oftenmanifest as cut-marks on the blanket 124 caused by the edges of theprint media as the number of impressions increases. When the amount ofwear exceeds a threshold for a given dimension on the blanket 124, awear defect is determined to be present outside of that dimension, andthe healthy area 300 is determined to be within that dimension.

FIGS. 5a, 5b, and 5c show example results of calculations made by theranking algorithm 208 to determine the presence of a wear defect and theresulting dimensions of the healthy area 300 of the blanket 124. Wear isthe cumulative thickness of print media 104 that has been impressed ontothe blanket 124, and is calculated as the thickness of the print media104 multiplied by the impressions count. The algorithm 208 considers awear defect to be present when the wear exceeds a threshold, which inthis example is 500,000 microns of accumulated thickness. In a firstcalculation, the algorithm determines if there is a wear defect based onthe number of impressions made by media according to the media lengths.Thus, using the blanket history data 218 shown in FIG. 4, the algorithm208 determines that for both the media lengths of 450 mm (from printjobs 1 and 3) and 420 mm (from print jobs 2, 4, and 5), the amount ofwear exceeds the 500,000 threshold. Accordingly, as shown in FIG. 5a ,wear defects are determined to be present at blanket lengths of 450 mmand 420 mm. That is, wear defects are determined to be present atlengths of 450 mm and 420 mm from the beginning point 301 (FIG. 3) ofthe blanket. In a second similar calculation, using the blanket historydata 218 shown in FIG. 4, the algorithm determines if there is a weardefect based on the number of impressions made by media according to themedia widths. As shown in FIG. 5b , a wear defect is determined to bepresent at a blanket width of 320 mm (from print jobs 1 and 3), but notat widths of 297 mm (from print jobs 2 and 5) and 266 mm (from print job4).

The dimensions of the healthy area 300 are then determined based on thelength and width dimensions that are found to have wear defects.Specifically, the length of the healthy area 300 is determined to be theminimum length defect (i.e., 420 mm) plus a tolerance for simplex jobsand duplex jobs. In this example, a simplex job tolerance is 3 mm, and aduplex job tolerance is 10 mm. Likewise, the width of the healthy area300 is determined to be the minimum width defect (i.e., 320 mm) plus awidth tolerance. In this example, the width tolerance is 6 mm.Accordingly, as shown in FIG. 5c , the healthy area 300 of the blanket124 is determined to be a length of 423 mm and width of 326 mm forsimplex print jobs, and a length of 430 mm and width of 326 mm forduplex print jobs.

It is noted that other criteria and methods can be used to determine thehealthy area 300 of an image transfer blanket 124, and that thosedescribed above with respect to FIGS. 4 and 5 are provided by way ofexample only. For example, other criteria for determining wear defectsand a healthy blanket area can include monitoring which areas of theblanket 124 receive ink and which areas do not receive ink for eachprint job/image printed. Blankets 124 have “image memory”, and they tendto age differently and be damaged in areas where little or no ink isbeing transferred. The image memory is a measurable condition thatprovides another example of how the healthy area 300 of a blanket can bedetermined.

Referring again to FIG. 3, in addition to the healthy area 300 of theimage transfer blanket 124 and the image area 302, an image risk area(IRA) 304, and a potential damage area (PDA) 306, are also shown. Likethe healthy area 300, the IRA 304 and PDA 306 shown in FIG. 3 representgraphical illustrations that correspond with IRA 214 and PDA 216numerical values calculated and stored in the memory 202, as noted aboveregarding FIG. 2. As noted above, in the FIG. 3 example the image area302 and the print media 104 substrate area are assumed to be the samesize, as shown by the dashed line. For different print jobs 206, theimage area 302, print media 104 substrate area, IRA 304, and PDA 306 mayvary, but within a given print job 206, the image area 302, print media104 substrate area, IRA 304, and PDA 306 remain the same.

As noted above, the IRA 304 (214 in FIG. 2), and PDA 306 (216 in FIG.2), are the two factors whose values are calculated and considered bythe ranking algorithm 208 to prioritize the print jobs 206 in a printorder (i.e., a ranked job print order list 210). The IRA 304 is theamount of image area 302 that falls on the blanket 124 outside of thehealthy area 300 of the blanket. The PDA 306 is the amount of thehealthy area 300 of the blanket 124 that the image area 302 (print media104 substrate) does not cover. Thus, a print job 206 whose image area302 does not cover the entire healthy area 300 of the blanket 124,creates the potential to cause additional damage to the blanket in thePDA 306, which can further reduce the size of the healthy area 300.

The ranking algorithm 208 calculates the IRA 304 and PDA 306 of a printjob 206 using the image area 302 width (W) and length (L), and thehealthy area 300 width (W_(HA)) and length (L_(HA)), as shown in FIG. 3.Since the IRA 304 is the amount of image area 302 that falls outside ofthe healthy area 300 of the blanket 124, and the PDA 306 is the amountof the healthy area 300 of the blanket 124 that the image area 302(print media 104 substrate area) does not cover, the IRA and PDA arereadily calculated by algorithm 208 from equations as shown in thefollowing table.

TABLE Definitions: ΔW = W − W_(HA) ΔL = L − L_(HA) When: When: When:When: ΔW ≦ 0 & ΔL ≦ 0 ΔW > 0 & ΔL > 0 ΔW ≦ 0 & ΔL > 0 ΔW > 0 & ΔL ≦ 0IRA = 0 IRA = IRA = ΔL × W IRA = ΔW × L (W_(HA) × L_(HA)) − (W × L) PDA= PDA = 0 PDA = |ΔW| × L_(HA) PDA = |ΔL| × W_(HA) (W_(HA) × L_(HA)) − (W× L)

After calculating the IRA 304 and PDA 306 values for each print job 206,the ranking algorithm 208 sorts the print jobs first by the IRA 304values, from the smallest IRA to the largest IRA. Thus, a ranked printorder 210 is determined in which jobs with smaller IRA 304 values areranked ahead of (and will be printed before) jobs with larger IRA 304values. Where two or more print jobs 206 have an equivalent IRA 304value that falls within a tolerance (e.g., a tolerance of 100 mm²), thealgorithm next ranks or prioritizes those jobs amongst themselves basedon their PDA 306 values. Jobs with equivalent IRA values are ranked sothat jobs with smaller PDA values are ranked above jobs having largerPDA values. Thus, in circumstances where all print jobs 206 havedifferent IRA 304 values, the print jobs will be ranked based on theirIRA values alone, without resorting to the PDA values for ranking. Iftwo or more print jobs 206 have both equivalent IRA 304 values andequivalent PDA 306 values (e.g., within a tolerance of 100 mm²), thealgorithm 208 ranks the print jobs with the same priority such thattheir print order amongst themselves is irrelevant.

The ranked job print order list 210 enables the printing device 100 tocontinue printing on a partially defective image transfer blanket 124with a reduced risk that the printed output will show defects from theblanket 124. This allows print operators to extend the lifespan of imagetransfer blankets, which reduces costs and improves printing efficiency.

FIGS. 6, 7, and 8, show flowcharts of example methods 600, 700, and 800,related to implementing a print job ranking algorithm that ranks printjobs into a printing order based on a healthy area of an image transferblanket and the likelihood that each job will not incur visible printdefects when printed. Methods 600, 700, and 800, are associated with theexample implementations discussed above with regard to FIGS. 1-6, anddetails of the steps shown in methods 600, 700, and 800, can be found inthe related discussion of such implementations. The steps of methods600, 700, and 800, may be embodied as programming instructions stored ona non-transitory computer/processor-readable medium, such as memory 202of FIG. 2. In different examples, the implementation of the steps ofmethods 600, 700, and 800, is achieved by the reading and execution ofsuch programming instructions by a processor, such as processor 200 ofFIG. 2. Methods 600, 700, and 800, may include more than oneimplementation, and different implementations of methods 600, 700, and800, may not employ every step presented in the flowcharts. Therefore,while steps of methods 600, 700, and 800, are presented in a particularorder within the flowcharts, the order of their presentation is notintended to be a limitation as to the order in which the steps mayactually be implemented, or as to whether all of the steps may beimplemented. For example, one implementation of method 600 might beachieved through the performance of a number of initial steps, withoutperforming one or more subsequent steps, while another implementation ofmethod 600 might be achieved through the performance of all of thesteps.

Referring to FIG. 6, method 600 begins at block 602, where the firststep shown is to access a list of print jobs for printing. Such printjobs may be, for example, a group of print jobs stored in a memory of aprinting device. At block 604, method 600 continues with determining ahealthy area of a transfer media. In one example, determining a healthyarea of a transfer media includes calculating a cumulative thickness ofprint media that has been impressed upon an image transfer blanket. Animage risk area (IRA) is then calculated for each job in the list basedon the healthy area, as shown at block 606. Calculating the IRAcomprises determining an amount of an image area (i.e., print mediasubstrate) of a print job that falls outside of the healthy area. Atblock 608, the method 600 continues with ranking each job in a printorder according to its IRA. Ranking a print job comprises ranking thejob in the print order from lowest IRA to highest IRA, where a jobhaving the lowest IRA is ranked first in the print order and a jobhaving the highest IRA is ranked last in the print order. A potentialdamage area (PDA) is then calculated for each job in the list based onthe healthy area, as shown at block 610. Calculating a PDA comprisesdetermining an amount of the healthy area that an image area (i.e.,print media substrate) of a job does not cover. As shown at block 612,when a plurality of jobs have equivalent IRAs, the plurality of jobs isfurther ranked within the print order according to their PDAs. Rankingthe plurality of jobs with equivalent IRAs comprises ranking them in theprint order from lowest PDA to highest PDA, where a job with the lowestPDA is ranked above a job with the highest PDA. The method 600 concludesat block 614, with the step of controlling a printing device to printthe print jobs from the list of print jobs according to the print order.

Referring to FIG. 7, method 700 begins at block 702, where the firststep shown is to calculate a healthy area of an image transfer blanket.In one example, calculating a healthy area of an image transfer blanketcomprises calculating wear as a cumulative thickness of print mediaprinted on the image transfer blanket, determining that a defect ispresent in the image transfer blanket when the wear exceeds a threshold,and establishing a length dimension and width dimension of the healthyarea based on lengths and widths of the print media whose cumulativethickness caused the wear to exceed the threshold. The method 700continues at block 704 with calculating an image risk area (IRA). TheIRA is as an amount of an image area of a print job that falls outsideof the healthy area of the image transfer blanket. In one example, wherethe print job image area has width, W, and length, L, and the healthyarea has width, W_(HA), and length, L_(HA), the IRA is calculated froman equation selected from the group consisting of, IRA=0,IRA=(W_(HA)×L_(HA))−(W×L), IRA=(L−L_(HA))×W, and, IRA=(W−W_(HA))×L. Thechoice of which equation is used is determined by the differences inlengths and widths of the print job image area and the healthy area, asshown in the Table herein above. At block 706, the print job is rankedin a print order so that it is above other print jobs having larger IRAsand below other print jobs having smaller IRAs. As shown at block 708, apotential damage area (PDA) is calculated as an amount of the healthyarea that is not covered by the image area of the print job (i.e., printmedia 104 substrate area). In one example, where the print job imagearea has width, W, and length, L, and the healthy area has width,W_(HA), and length, L_(HA), the PDA is calculated from an equationselected from the group consisting of, PDA=0, PDA=(W_(HA)×L_(HA))−(W×L),PDA=|W−W_(HA)|×L_(HA), and, PDA=|L−L_(HA)|×W_(HA). The choice of whichequation is used is determined by the differences in lengths and widthsof the print job image area and the healthy area, as shown in the Tableherein above. As shown at block 710, where the IRA of the print job isthe same as an IRA of a second print job: the print job is ranked abovethe second print job when the PDA is smaller than a PDA of the secondprint job; the print job is ranked below the second print job when thePDA is larger than the PDA of the second print job; and, the print jobis ranked even with (i.e., the same as) the second print job when thePDA is the same as the PDA of the second print job.

Referring to FIG. 8, method 800 begins at block 802, where the firststep shown is to determine a healthy area of an image transfer blanket.At block 804, a list of print jobs is accessed. Each print job in thelist define an image area. For each print job, an image risk area (IRA)is determined that defines an amount of the image area that fallsoutside of the healthy area, as shown at block 806. Also, for each printjob, a potential damage area (PDA) is determined that defines an amountof the healthy area that is not covered by the image area, as shown atblock 808. At block 810, the print jobs are ranked in a print orderbased on the IRA and PDA of each print job. Ranking the print jobs basedon the IRA and PDA comprises, first, ranking the print jobs fromsmallest IRA to largest IRA, and second, where two or more print jobshave equivalent IRAs, ranking the two or more print jobs from smallestPDA to largest PDA.

What is claimed is:
 1. A non-transitory processor-readable mediumstoring code representing instructions that when executed by a processorcause the processor to: access a list of print jobs for printing;determine a healthy area of an image transfer blanket, wherein thehealthy area represents an area of the image transfer blanket that is totransfer images from a photo imaging plate to a print media withouttransferring defects from the image transfer blanket to the print media;for each print job in the list of print jobs, calculate an image riskarea (IRA) based on the determined healthy area, wherein the IRA is anamount of an image area of the print job that falls on the imagetransfer blanket outside of the healthy area of the image transferblanket; rank each print job in the list of print jobs in a print orderaccording to the calculated IRA of the print job; and control a printingdevice to print the print jobs from the list of print jobs according tothe ranked print order.
 2. The non-transitory processor-readable mediumas in claim 1, wherein to rank each print job, the instructions are tocause the processor to rank the print job in the print order from lowestIRA to highest IRA, where a print job with the lowest IRA is rankedfirst in the print order and a job with the highest IRA is ranked lastin the print order.
 3. The non-transitory processor-readable medium asin claim 1, wherein the instructions further cause the processor to: foreach print job in the list, calculate a potential damage area (PDA)based on the healthy area, wherein the PDA of a print job is an amountof the healthy area of the image transfer blanket that the image area ofthe print job does not cover; and when a plurality of print jobs haveequivalent IRAs, further rank the plurality of print jobs within theprint order according to the calculated PDAs of the print jobs.
 4. Thenon-transitory processor-readable medium as in claim 3, wherein tofurther rank the plurality of jobs according to the calculated PDAs, theinstructions are further to cause the processor to rank the plurality ofprint jobs in the print order from lowest PDA to highest PDA, where aprint job with the lowest PDA is ranked above a print job with thehighest PDA.
 5. The non-transitory processor-readable medium as in claim1, wherein to determine a healthy area of an image transfer blanket, theinstructions are further to cause the processor to: calculate acumulative thickness of print media that has been impressed upon theimage transfer blanket.
 6. A non-transitory processor-readable mediumstoring code representing instructions that when executed by a processorcause the processor to: calculate a healthy area of an image transferblanket, wherein the healthy area represents an area of the imagetransfer blanket that is to transfer images from a photo imaging plateto a print media without transferring defects from the image transferblanket to the print media; calculate an image risk area (IRA) as anamount of image area of a print job that falls outside of the healthyarea of the image transfer blanket; rank the print job in a print orderso that the print job is above other print jobs having larger IRAs andbelow other print jobs having smaller IRAs; and control a printingdevice to print the print jobs according to the ranked print order. 7.The non-transitory to him processor-readable medium as in claim 6,wherein the instructions further cause the processor to: calculate apotential damage area (PDA) as an amount of the healthy area not coveredby the image area of the print job; and where the IRA of the print jobis the same as an IRA of a second print job, rank the print job abovethe second print job when the PDA is smaller than a PDA of the secondprint job, below the second print job when the PDA is larger than thePDA of the second print job, and even with the second print job when thePDA is the same as the PDA of the second print job.
 8. Thenon-transitory processor-readable medium as in claim 6, wherein tocalculate a healthy area the instructions are further to cause theprocessor to: calculate wear as a cumulative thickness of print mediaprinted on the image transfer blanket; determine a defect in the imagetransfer blanket when the wear exceeds a threshold; and establish alength dimension and width dimension of the healthy area based onlengths and widths of print media whose cumulative thickness caused thewear to exceed the threshold.
 9. The non-transitory processor-readablemedium as in claim 6, wherein the image area of the print job has width,W, and length, L, and the healthy area has width, W_(HA), and length,L_(HA), and the IRA is calculated from an equation selected from thegroup consisting of, IRA=0, IRA=(W_(HA)×L_(HA))−(W×L), IRA=(L−L_(HA))×W,and, IRA=(W−W_(HA))×L.
 10. The non-transitory processor-readable mediumas in claim 7, wherein the image area of the print job has width, W, andlength, L, and the healthy area has width, W_(HA), and length, L_(HA),and the PDA is calculated from an equation selected from the groupconsisting of, PDA=0, PDA=(W_(HA)×L_(HA))−(W×L), PDA=|W−W_(HA)|×L_(HA),and, PDA=|L−L_(HA)|×W_(HA).
 11. A non-transitory processor-readablemedium storing code representing instructions that when executed by aprocessor cause the processor to: determine a healthy area of an imagetransfer blanket, wherein the healthy area represents an area of theimage transfer blanket that is to transfer images from a photo imagingplate to a print media without transferring defects from the imagetransfer blanket to the print media; access a list of print jobs, eachprint job defining an image area; for each print job, determine an imagerisk area (IRA) that defines an amount of the image area that fallsoutside of the healthy area; for each print job, determine a potentialdamage area (PDA) that defines an amount of the healthy area not coveredby the image area; rank the print jobs in a print order based on the IRAand PDA of each print job; and control a printing device to print theprint jobs according to the ranked print order.
 12. The non-transitoryprocessor-readable medium as in claim 11, wherein to rank the print jobsin a print order based on the IRA and PDA of each print job theinstructions are further to cause the processor to: first, rank theprint jobs from smallest IRA to largest IRA; and second, where two ormore print jobs have equivalent IRAs, rank the two or more print jobsfrom smallest PDA to largest PDA.